Many guns and firearms use ammunition provided in pre-loaded magazines, and accordingly are configured with integrated or built-in magazine holders. A magazine holder is a well or hollow compartment in the lower receiver of the frame where the firearm is gripped by the operator. The well has a bottom opening, and an interior sized and shaped to snugly hold a magazine. When the ammunition in the magazine has been discharged, the operator removes the empty magazine and inserts a freshly loaded magazine into the well through the bottom opening.
Firearm magazine well openings are usually just slightly larger than the cross-section of the magazines the firearms are designed to receive. As a result, in practice the magazines need to be carefully aligned with the well openings before insertion. This requires a degree of attention and time on the part of the operator. In firearm applications involving law enforcement or the military, any extra time spent replacing magazines may expose the operator to danger. In other applications such as sport shooting, the extra time may be inconvenient and counterproductive.
Various attempts have been made to improve magazine wells, to make it easier and quicker to insert a fresh magazine. One approach is to alter the magazine well opening by attaching an extension or add-on to the firearm frame. The frame or magazine well extensions generally include an opening larger than the magazine well opening, and provide a beveled edge around the opening to help guide a magazine into the holder. In some cases, particularly in pistols, they also increase the length of the magazine well by providing a frame extension that is bolted to the main spring housing of the pistol.
Some machining of the gun frame is usually required in order to attach the magazine well extension. For example, bores may need to be drilled in the gun frame so that the extension can be attached by screws. Other extensions may be attached by welding. As a result, the services of a skilled person such as a gunsmith, machinist, or welder are usually required, which necessarily increases the cost and complication of the extension.